1. Field of the Invention
The present invention relates to a nonaqueous electrolyte battery, and a battery pack and a vehicle using the nonaqueous electrolyte battery.
2. Description of the Related Art
Research and development of a nonaqueous electrolyte battery comprising a negative electrode containing metallic lithium, a lithium alloy, a lithium compound or carbonaceous materials have been actively advancing as a high energy density battery or high power density battery. A lithium ion battery comprising a positive electrode containing LiCoO2 or LiMn2O4 as an active material and a negative electrode containing a carbonaceous material for absorption/release of lithium ions has been put into practical use. Metal oxides or alloys as substitutes of the carbonaceous material in the negative electrode have been also studied.
A copper foil is used for a current collector of these negative electrodes. However, the discharge capacity rapidly decreases when the nonaqueous electrolyte battery having the current collector made of copper foil is overdischarged since a dissolving reaction of the copper foil is accelerated by an increase in potential of the negative electrode. Accordingly, a protective circuit for preventing the battery from being overdischarged is provided in the nonaqueous electrolyte battery. However, the nonaqueous electrolyte battery having the protective circuit was disadvantage in terms of the energy density.
Accordingly, there has been proposed a nonaqueous electrolyte battery comprising a negative electrode current collector containing aluminum or an aluminum alloy, and a negative electrode including a negative electrode layer containing at least one negative electrode active material selected from the group consisting of a metal, an alloy or a compound for absorption/release of lithium ions, as described in JP-A 2002-42889 (KOKAI). This structure can provide a nonaqueous electrolyte battery improved in energy density and overdischarge cycle performance.
However, the nonaqueous electrolyte battery described in JP-A 2002-42889 (KOKAI) involves a problem in the performance under a high temperature environment.
JP-A 8-298137 (KOKAI) discloses using an electrolytic aluminum foil having a roughened surface and a specific capacitance of 50 μF/cm2 or more as a current collector of the positive electrode of a secondary battery using a nonaqueous electrolytic solution. JP-A 8-298137 (KOKAI) describes that this current collector may be used for the negative electrode.
On the other hand, JP-A 11-86875 (KOKAI) relates to a positive electrode for a nonaqueous secondary battery using a liquid electrolyte or a polymer electrolyte. An aluminum foil processed to have a specific capacitance of 5 to 40 μF/cm2 by etching is used as the current collector of the positive electrode described in JP-A 11-86875 (KOKOAI).